Building dialogues between ethnobiology and chemistry: the process of elaboration of guayacán ink (Caesalpinia paraguariensis) among the Wichís of the Gran Chaco

Abstract

Ethnobiology studies the links between humans and the natural environment. The axis guiding the studies is the understanding of how cultures conceptualize, classify, feel and use nature. The incorporation of information from other fields of the exact and natural sciences has been used in ethnobiology to analyze, for example, the influence that material characteristics have on the selection of different raw materials. Likewise, and although little explored so far, chemical information allows a deeper understanding of different processes, such as the ways of elaboration of ferments, dyes or tanning techniques. In order to exemplify the above, this paper analyzes the change in the elaboration of guaiacan fruit dye (Caesalpinia paraguariensis) within the Wichí community of Tres Pozos (Formosa, Argentina), from an approach that complements ethnobiological information with chemical analysis. This is a dye that the Wichís of the Gran Chaco have been using since ancient times to dye cháguar (Bromelia spp.) yarns black, and for which the method of elaboration has changed drastically over time: from mordanting with black mud to the absence of mordanting and, in replacement, maceration for long periods of time, a technique of difficult execution that the weavers describe as "fermentation". Chemically, the dye is composed mainly of hydrolyzable yellow-brown tannins that form complexes with black iron. While in the past the iron came from the mordant (mud), nowadays it is contributed gradually by the oxidized vessels; hence, if it is macerated for short periods of time and/or in vessels without surface oxide, the dyeing does not result in the desired color. The inclusion of chemical information allowed to broaden the understanding of the ways of elaboration of this dye, including the current difficulties of execution.